Synchronous-type fluid-blast circuit interrupters



Nov. 2, 1965 F. KESSELRING 3,

SYNCHRONOUS-TYPE FLUID-BLAST CIRCUIT INTERRUPTERS Filed March 27, 1961 2Sheets-Sheet l Fig. 2.

I z A A u ,U 2 .u I i b a l q I A; t /t '0 2 N *3 t r 'r Fig. 3.

LI HIGH 2 PRESSURE 3 WITNESSES INVENTOR Frirz Kesselring.

BY Q L m ,2 W

' ATTORNEY Nov. 2, 1965 F. KESSELRING 3,215,804

SYNCHRONOUS-TYPE FLUID-BLAST CIRCUIT INTERRUPTERS Filed March 27. 1961 2Sheets-Sheet 2 example, in oil circuit breakers.

United States Patent 3,215,804 SYNCHRONOUS-TYPE FLUID-BLAST CIRCUITINTERRUPTERS Fritz Kesselring, Kusnacht, Zurich, Switzerland, assignorto Siemens-Schuckertwerke Aktiengesellschaft, Erlangen, Germany, acorporation of Germany Filed Mar. 27, 1961, Ser. No. 98,522 Claimspriority, application Germany, Mar. 30, 1960, S 67,800, S 67,801, S67,802 3 Claims. (Cl. 200-148) This invention relates tosynchronous-type fluid-blast circuit interrupters in general and, moreparticularly, to improved interrupting structures therefor.

A general object of the present invention is to provide an improvedsynchronous-type fluid-blast circuit interrupter which will be highefficient and which will utilize a minimum quantity of arc-extinguishingfluid.

Another object of the present invention is to provide an improvedcompressed-gas circuit interrupter in which the application of thearc-extinguishing medium is dependent upon a predetermined reduction inmagnitude of the value of the instantaneous current being interrupted.

Still a further object of the present invention is the provision ofimproved compressed-gas circuit-interrupting structures in which moreeffective use of the gas-blast medium is obtained by the employment ofsynchronouslyoperated valve structures.

In United States patent application filed March 22, 1965, Serial No.97,656 by Fritz Kesselring and Lutz Seguin and assigned to the assigneeof the instant application, there are disclosed and claimed novel-typesynchronous operators particularly suitable for synchronously-operatedcircuit-interrupting devices. It is a further object of the presentinvention to utilize the principles set forth in the aforesaid patentapplication rendering them highly efficient as applied tocircuit-interrupting devices.

Additional objects and advantages will readily become apparent uponreading the following specification, taken in conjunction with thedrawings, in which:

' FIGS. 1 and 2 illustrate time graphs of energy input into circuitinterrupters of conventional type and those embodying features of thepresent invention during the circuit-interrupting operaion;

FIG. 3 is a somewhat diagrammatic view taken in vertical cross-sectionthrough a compressed-gas-type of circuit interrupter embodying featuresof the present invention, the contact structure being illustrated in thepartially open circuit position;

FIGS. 4-7 illustrate novel types of blast-valve arrangements embodyingfeatures of the present invention; and,

FIG. 8 illustrates a perspective view of a double-valve arrangementembodying features of the present invention.

Referring to the drawings, and more particularly to FIGS. 1 and 2thereof, it will be noted that the stresses exerted upon theinterrupting chambers of electric circuit interrupters are determined inaccordance with their design by the maximum interrupting are power orthe maximum arc work dissipated. The latter case occurs when thepressure produced by the arc cannot be continuously equalized throughoutthe breaker, as it happens to be, for

As it is known, the interrupting work A is given by the equation:

t 215:1 b idi where:

=instantaneous value of the arcing voltage, i =instantaneous value ofthe current, and t =arcing time.

It has been found that the mean value of the current i and, mostimportantly, the arcing time t can be reduced by control ofsynchronization. In single-phase circuit breakers the control ofsynchronization is applied in a relatively easy manner. On the otherhand, in the case of polyphase circuit breakers, for frequencies of 50or cycles, considerable difliculties are often encountered. This factcan be seen at once in that the mass of the moving system necessary forlarge rated currents cannot be brought satisfactorily to the separateddistance necessary for arc-extinguishing action in a sufiiciently shorttime, for example, in 1 millisecond. Also, the current wave is not assingularly defined as in the case of single-phase circuit breakers.When, for example, a two-phase arcing short circuit changes shortly,before passage through current zero, into a three-phase short circuit,the current wave changes considerably, which may lead to faultyswitching. Furthermore, the maintenance of so-called flashoverinterruptions under control presents considerable difficulties becauseof the then resulting extraordinary high are power.

It is known that the value of the arc voltage depends very much on whatkind of effect the quenching medium has upon the arc. If the arc isdrawn in a still, atmosphere, then the arc-voltage gradient isapproximately 20 to 30 volts/centimeter. On the other hand, if the arcis subjected to, for example, intensive axial blasting, or, if in thegas-vapor atmosphere surrounding the are under high pressure, thereoccurs a sudden expansion, then the arc-voltage gradient reaches 200volts/centimeter, and more. In the case of the transition from little,or only slightly affected arcs, to strongly affected arcs, thearcvoltage gradient and the corresponding arc voltage changes by afactor of approximately 10. v

The present invention, in part is concerned with a fluidblast circuitbreaker, especially suitable for alternating current interruptions, inwhich, as contracted with known breakers, the interrupting work to bedissipated is considerably reduced. The present invention is, in part,distinguished by the fact that there is provided a control, which makesthe quenching medium, serving for arc-extinguishing action in the caseof arbitrary interruption times, effective only when the current isdecreasing, specifically 0.5 to 2.0 milliseconds before the currentpasses through current zero.

The advantages of fluid-blast circuit breakers constructed in accordancewith the present invention can be seen clearly from a comparison ofFIGS. 1 and 2 of the drawings. In both figures i is theinterruptedcurrent, m, is the arc voltage, and l is the arcing time. Thecontact separation follows arbitrarily at instant t At instant t thereoccurs the first passage of the current through current zero. However,the contact separation is still so small that the interruption of thearc does not take place. At the instant t the necessary separationdistance is assumed t-o'be reached and, therefore, the arc-quenchingaction should follow, whereby it is assumed that in both cases themaximum arc voltage ,u occurs. Breakers of known design provide, shortlyafter the contact separation, immediately intensive arc-extinguishingaction, which leads to increased arc voltage ,u On the contrary, in thecase of circuit breakers constructed according to the present invention,intensive effect upon the arc can be found only in intervals t -t andt2-t3. The arc voltage will, therefore, remain very small in magnitudeup to the instant t and increase correspondingly-only toward the passagethrough current zero t This results in that the interrupting work,represented by the shaded area A as illustrated in FIG. 2, is only afraction of the interrupting work A as shown in FIG. 1, beingapproximately /5 in the illustrated example taken from an actual case.In addition, there exists also a considerably lower maximum are power1:1 which amounts to approximately one-half of N Correspondingly, thestresses from pressure in the case of circuit breakers, constructed inaccordance with the present invention, are considerably lower, whichmakes possible a lighter design of the interrupting chamber and leadsconsequently to lower production costs.

Still a further improvement can be obtained by constructing circuitbreakers in accordance with the present invention in that the intensityof quenching can be made dependent upon the magnitude of rate ofdecrease of the interrupted current, that is, (-di/dt/). As well known,the quenching intensity must be the greater the greater is theinstantaneous rate of change of the interrupted current immediatelybefore the passage through current zero, and the greater is the slope ofthe recovery voltage. The latter is generally given by the networkconditions and the magnitude of the interrupted short-circuit current.For a higher short-circuit current and thereby for a higher rate ofchange of the short-circuit current, there corresponds most of the timealso a higher slope of the recovery voltage, because the inductance ofthe oscillating circuit at higher short-circuit intensities iscorresponding 1y lower. If also the intensity of arc quenching is madegreater, the greater is the rate of decrease of the interrupturedcurrent, then it can be expected that the arc quenching takes place withless possible effort, and also lowest overvoltage over the entirecurrent range from very small currents up to full short-circuit currentintensities. As well known, for example, in disconnecting a transformerrunning at no-load, a very high overvoltage occurs, because thequenching intensity is very often too high relative to the small no-loadcurrent, for example, only 10 amperes. The are then interrupts too soon,which results in an instantaneous release of the large amount ofmagnetic energy stored in the transformer under a stronger build-up ofthe overvoltage. In case of compressed-gas circuit breakers, a matchingof the intensity of interrupting conditions to the slope of currentshortly before passage through current zero has an additional advantagein that the consumption of compressed air at normal switching operationsis considerably reduced.

FIG. 3 shows by way of example a form of construction of compressed-gascircuit interrupter constructed in accordance with the presentinvention. With reference to FIG. 3, the reference numeral 1 indicatesan interrupting chamber in the form of an insulating cylinder. At thetop, the interrupting chamber 1 supports the interrupting nozzle contact2 having a terminal lead 3. The

bottom of the insulating cylinder 1 is closed by a closure cap 4 havinga second terminal lead 5. The reference numeral 6 indicates cooperablesliding contacts which carry the current from the terminal lead to themovable contact rod 7. The compressed gas is brought into theinterrupting chamber 1 through an electrically actuated valve 8 and aninsulating blast tube 9. The reference numeral 10 indicates a rotatablevalve damper shown in the open position in FIG. 3. It is actuated by amoving coil or armature 11, which rotates in the field of anelectromagnetic system 12 excited by the interrupting current, as setforth in the aforesaid United States patent application.

The reference numeral 13 denotes an operating cylinder, which isconnected through a tube 14 with the insulating blast tube 9. A piston15, movable within the operating cylinder 13, is acted upon by acompression spring 16. An insulating operating rod 18 is supported upona pivot 17, and is coupled with the piston 15 through a driving link 19.The rod 18 is also connected with the movable contact rod 7 by means ofa pivot pin 20. In the open-circuit position, shown by the dotted lines7a, the insulating operating rod 18 is held by a rotatable latch 21against the biasing action exerted by the compression spring 16.

The circuit interrupter, generally designated by the reference numeral22 and set forth in FIG. 3, functions in the following manner: At anarbitrary instant t the electromagnetically actuated valve 8 is assumedto be opened. This action results in exposing the piston 15 to theentering blast of compressed gas, which will cause the piston 15 to movedownwardly against the biasing action exerted by the compression spring16 until the movable contact rod 7 reaches the illustrated open position7a of completed interruption. Now, if the current is increasing duringthis process, then an induced current will flow through the moving coilof armature 11, which will, together with the flux in the magneticsystem 12, produce in the air gap a torque, which causes the rotatablevalve damper 10 to turn to a closed position. In this connection, it isto be noted that the magnetic circuit 12 encompasses the main currentpath L L and consequently has flux generated therein corresponding tothe line current. As a result, if at first the compressed air cannotenter the interrupting chamber 1 to blast the arc, the are 23 burns witha much lower arc voltage than would be the case otherwise. Now, if themain current begins to decrease, then the current induced in the movingcoil 11 will change its sign as set forth in the aforesaid United Statespatent application, Serial No. 97,656. The torque is then reversed, andthe valve damper 10 will now assume the illustrated open position. Byutilization of saturation of the magnetic system 12,

it can be obtained that the current induced in the moving coil 11 beginsto flow 0.5 to 2 milliseconds before the passage of the current throughcurrent zero. Now, at this time the compressed air may enter theinterrupting chamber 1 from the blast tube 9 and act intensively uponthe arc 23a drawn within the nozzle 2, thereby bringing aboutinterruption of the arc 23a and consequent circuit interruption.

If, on the contrary, a transformer operating at no-load should bedisconnected, and if, as a result of build-up of overvoltage causing ashort circuit shortly before the no-load current of the transformerpasses through current zero, then the current immediately sharplyincreases. This results in the situation whereby the valve damper 10will be instantly moved into the closed position by the moving coil 11,by which action the passage of the flowing gas upon the are 23a isstopped. The are has a high current intensity but a very low arcingvoltage. Later, when the current again begins to decrease, the valvedamper 10 will then open and the arc quenching action will follow.

If the valve damper 10 is supported upon the rotatable shaft 11a of themoving armature 11, then it can be obtained in a relatively simplemanner that the valve damper 10 opens wider the more quickly the linecurrent decreases toward current zero. As a result, it is possible tomatch or correlate the intensity of quenching to the intensity of theinterrupted current, especially to the slope with which it passesthrough current zero. For this purpose, it may be suitable to establishthe normal at rest position of the valve damper 10 in such a positionthat the minimum intensity of quenching, necessary for interruption ofcurrents in the normal operating range, is provided. If now highercurrents are to be interrupted, then automatically a correspondinglylarger movement of the valve damper 10 takes place, so that again theintensity of quenching is adjusted to the prevailing conditions.

If, for example, in the case of interrupters using liquids, an expansionshould be introduced, then blocking of a valve 10 during increasingcurrent can be released when the current begins to decrease towardcurrent zero, in which case it may be suitable to introduce theexpansion shortly before the passage of the current through currentzero.

The advantage of circuit breakers constructed according to the presentinvention consists largely in that the breaker mechanism itself can bebuilt in the generally conventional manner, and does not need to moveespecially fast as is necessary in the case of conventional synchronizedbreakers. The control is limited entirely to the matching or correlatingof the intensity of interrupting action to the prevailing conditions,which can be done at a small cost. The interrupting capacity of breakersof the type built according to the present invention can be, although atapproximately the same production cost as conventional breakers,increased to several times the value so far obtained.

It is known in the valve art to provide arrangements including arotatable wing-type valve adapted to be electrically operated anddisposed within a cylindrical opening. With valves of this type it isdesirable that the valve, when closed, have a very tight fit and, whenopened, permit optimum flow conditions to take place. Opening of suchvalves is usually effected by rotating the valve about 90. Theelectrical drive may comprise either a motor or a magnetic drive. If itis desired to provide valves which have a short operating time fromclosed condition to open condition, or vice versa, of less than $4 of asecond particularly less than one millisecond, certain problems areencountered at once. Such extremely fast-acting valves are needed, forexample, for compressed-fluid electrical switches in which arcextinction is eifected by a flowing medium. In such switches, or circuitbreakers it is necessary that the valves be operated, for example, at acertain instant, within one current halfcycle. It is not absolutelynecessary in circuit breakers for the valve to establish a perfect sealwhen closed, for a small amount of leakage is not objectionable sincethe quick-acting valve usually has connected in series therewith anothertightly-closed valve, such as indicated by the reference numeral 27 inFIG. 4, which may be of conventional design.

According to one aspect of the present invention as shown in FIGS. 4 and5, the valve arrangement including at least one electrically-operatedrotatable wing valve disposed in a cylindrical opening is characterizedin that the cross-section of the rotary wing, or wings perpendicular tothe axis of rotation is biangular for obtaining opening and closingtimes of less than milliseconds, the width b of the axial sealingsurfaces of the rotatable wing amounting to only a fraction of themaximum wing thickness d, and the width of the rectangular valve openingB being no more than equal to the radius r of the rotatable wing.

In FIGS. 4 and 5 of the drawings, a valve arrangement, according to theinvention, is shown schematically in the closed and open positions,respectively. FIGS. 6 and 7 illustrate a similar valve arrangement whichoffers particularly little resistance to flow, and FIG. 8 shows a doublevalve arrangement including two rotatable wing valves actuated by asingle moving-coil system.

In FIGS. 4 and 5, the reference numeral 31 designates a cylindricalvalve casing and the reference numeral 32 indicates the wing-valvecomprising two plates 33 and 34 rigidly connected to the shaft 35. Theaxial sealing surfaces are indicated at 36. The reference numeral 37designates rectangular inlet, and the reference numeral 38 designatesthe rectangular outlet. In FIG. 4 of the drawings, the pressure P actsupon the upper surface -33 of the rotatable wing valve 32. Since thepressure distribution relative to the axis of rotation 35 issymmetrical, substantially no resultant torque is applied to thewing-valve 32.

FIG. 5 shows the valve in its fully opened position, and this figurealso illustrates the fact that the torsional moment, or torque actingupon the wing valve 32 is zero. Contrary to the positioning of the valve32 shown in FIG. 4 in which there exists a stable equilibrium, theequilibrium in the open position, as shown in FIG. 5 is unstable.

As soon as the wing valve is moved somewhat from its symmetricalposition, it tends to move to its closed position, and the maximumclosing force is effective approximately in the position indicated bybroken lines 32a in FIG. 5. Accurate measurements taken with the valvea-rrangement according to FIG. 4 and involving the values r=6millimeters, B=5 millimeters, d=3 millimeters, and a wing height of 30millimeters indicated at 1 to 6 atmospheres overpressure on the inletside, result in a maximum torque in the closingdirection of about pond(gram weight) centimeters, that is, an extraordinarily small valuewhich, however, is obtainable only when ball bearings are being used.

The width of the axial sealing surface of the rotatable wing valve was11:12 millimeters, and the sealing gap amounted to about millimeter. Theresultant leakage loss at 6 atmospheres was 2 cmF/ms. relative to normalpressure and normal temperature. With a gap thickness of 1 millimeter,it was possible to reduce the leakage loss to 0.9 .cm. /mS. Sealing canfurther be improved by providing at least along the axial sealingsurfaces of the rotatable wing sealing strips, which are biasedoutwardly, such as used, for example in rotary-piston type motors.

The embodiment illustrated in FIGS. 4 and 5 of the drawings has thefollowing advantages: The moment of inertia of the rotatable Wing valve32 is very small. Despite this, however, the stability is high due tothe boxtype construction. In order to fully open the valve, an angularmovement of the Wing only of a/2 is required. The torque necessary tomove the rotatable wing is very small. The resistance to flow of theopened valve is negligible. The use of wings having a height which issubstantially larger than their diameter makes it possible to obtainlarge cross-sectional flow areas with the valves of minimum dimensions.

FIGS. 6 and 7 illustrate an embodiment of the invention providing avalve arrangement for still better flow conditions. The rotatable wing42, which is movable within the casing 41 has an airfoil or streamlinedprofile. It may be formed, together with the shaft 43, by diecastin'g,for example, from an aluminum or magnesium alloy, the moment of inertiabeing further reduced by the axial openings 44. Furthermore, the casing41 may have dis-posed therein liners 45 and 46, as shown in FIG. 7,which are favorable to the streamline fiow of the medium.

FIG. 8 shows an embodiment of the invention utilizing valves 51 and 52of the type illustrated in FIGS. 4 and 5. Valve 51 is shown in its openposition, whereas valve 52 is shown in its closed position. Indicatedgenerally at 53 is a moving-coil system, the moving coil 54 of which issecured to the common shaft 55. The coil ends of coil 54 extend to theslip rings 56 and 57 and are connected through brushes 58 and 59 and aswitch 60 to a battery 61. The pole pieces of the moving-coil system areindicated at 62 and 63.

As the double throw switch 60 is moved from the center position,indicated by broken lines, to the upper position, current will flowthrough coil 54 in the direction indicated by the arrow, said current,together with the airgap induction producing a torque which causes thevalve 51 to be moved to its closed position and valve 52 to be moved toits open position.

Referring to FIG. 8, the rotary wing of valve 51 tends to move clockwiseto its closed position, whereas the rotary wing of valve 52 tends tomove counterclockwise also to its closed position, as shown. It is,therefore, apparent that the two torques of the rotary wings 51, 52substantially cancel each other. Movement of switch 60 to its lowerposition effects a reversal of the current flowing through coil 54,which, in turn, also reverses the torque. Thus, the two rotary wings ofvalves 51 and 52 return to the position shown.

Tests have proven that with an arrangement such as shown in FIG. 8, itis readily possible to effect movement 7 through the angle a/ 2 (FIG. 4)in less than l millisecond. The moment of inertia of one rotary wingincluding the shaft amounts to only about of the moment of inertia ofthe moving coil 54.

In one practical example, the main driving torque of the moving-coilsystem amounted to approximately 12 kpcm., whereas the resultant maximumcounter-torque acting upon the rotary Wings amounted to only about 0.03kpcm., that is, to only 2.5% of the driving torque, at 6 atmospheres ofover-pressure.

The battery 61 may be replaced by a charged condenser, which, whendischarged, causes a very high impulselike current to flow through themoving coil 54. Furthermore, the permanent magnet system 62 and 63 maybe replaced by an unsaturated, or saturated alternating-current magnet.If this is the case, and if coil 54 is supplied from a source of directcurrent, the rotary wings will oscillate at the frequency of thealternating current.

If it is desired to use the valve arrangement according to the inventionfor the control of fluid-blast circuit breakers, it is desirable toenergize the magnetic system 62 and 63 in dependency upon the current tobe interrupted, Whereas the moving coil 54 should be supplied with acurrent which may be proportional, for example, to the changing rate ofthe current to be interrupted. In this manner, it is possible to causevalve 51 to open only when the current decreases, particularly shortlybefore the zero passage of the current, and to be closed during theincrease of the current, during Which period the circuit breaker isvented by the valve 52. In view of the extraordinarily short responsetime of these valves 51 and 52, the valve arrangement embodying theinvention' may be used advantageously in connection with control andregulating systems.

Although there have been illustrated and described specifiic structures,it is to be clearly understood that the same were merely for the purposeof illustration, and that changes and modifications may readily be madetherein by those skilled in the art, without departing from the spiritand scope of the invention.

I claim as my invention:

1. A compressed-gas circuit interrupter including a stationarynozzle-type contact and a cooperable movable rod contact separable toestablish an arc, a source of highpressure gas, blast-valve meansincluding an electromagnetically-actuated valve (8) and a seriesrotatable blastvalve (10), piston means interposed between said twovalves and operable to effect opening motion of the movable rod contact,and a synchronous operator correlating the opening of therotatableblast-valve ('10) with the magnitude of the slope of the rateof change of currents, whereby a more intensive gas blast will beobtained for higher magnitude fault currents than for loadcurrentinterruption.

2. A compressed-gas circuit interrupter including a stationarynozzle-type contact and a cooperable movable rod contact separable toestablish an arc, a source of highpressure gas, blast-valve meansincluding an electromagnetically-actuated valve (8) and a seriesrotatable blastvalve (10), piston means (15) interposed between said twovalves and operable to effect opening motion of the movable rod contact,a synchronous operator corrleating the opening of the rotatableblast-valve (10) with the magnitude of the slope of the rate of changeof currents, Where'- by a more intensive gas blast will be obtained forhigher magnitude fault currents than for load-current interruption, saidsynchronous operator including a magnetic circuit energized independence upon the current to be interrupted, and a moving coil elementtraversed by a current dependent upon the rate of change of the currentto be interrupted. I

3. The combination according to claim 1, wherein a pivotally-mountedoperating lever (18) is connected to said movable rod contact and isactuated by the piston means, and the piston means is biased to theclosed contact position.

References Cited by the Examiner UNITED STATES PATENTS 443,326 12/90Leverich 251-305 1,267,898 5/18 Parish 251-305 1,332,000 2/20 Pfau251-305 2,222,719 11/40 Prince 200148 2,365,131 12/44 Amer et al. 2001482,496,553 2/50 Littlefield 1375 95 2,617,638 11/52 Udale 2513052,672,541 3/54 Paul 200-148 2,356,480 10/58 Westerhoff 200-148 3,049,3358/62 Daumy et al. -a 251-305 FOREIGN PATENTS 590,555 1/ Canada.

408,175 4/34 Great Britain.

379,301 3/40 Italy.

BERNARD A. GILHEANY, Primary Examiner.

MAX L. LEVY, ROBERT K. SCHAEFER, Examiners.

1. A COMPRESSED-GAS CIRCUIT INTERRUPTER INCLUDING A STATIONARYNOZZLE-TYPE CONTACT AND A COOPERABLE MOVABLE ROD CONTACT SEPARABLE TOESTABLISE AN ARC, A SOURCE OF HIGHPRESSURE GAS, BLAST-VLAVE MEANSINCLUDING AN ELECTROMAGNETICALLY-ACTUATED VALVE (8) AND A SERIESROTATABLE BLASTVALVE (10), PISTON MEANS (15) INTERPOSED BETWEEN SAID TWOVALVES AND OPERABLE TOEFFECT OPENING MOTION OF THE MOVABLE ROD CONTACT,AND A SYNCHRONOUS OPERATOR CORRELATING THE OPENINGS OF THE RORTATABLEBALST-VALVE (10) WITH THE MAGNITUDE OF THE SLOPE OF THE RATE OF CHANGEOF CURRENTS, WHEREBY A MORE INTENSIVE GAS BLAST WILL BE OBTAINED FORHIGHER MAGNITUDE FAULT CURRENTS THANFOR LOADCURRENT INTERRUPTION.